in_xsf pre-wxWidgets v0.1

Most of the fixes so far are for the NCSF Winamp plugin, though one backported patch is for all four plugins.

General notes:

• File path parsing backports - fixes Unicode handling in file paths/directories - filenames themselves were fine, however. Commits: 1e52dd4, 98bc2ff

NCSF:

• Reverted uint32_t to uint16_t - fixes some album handling issues as uint32_t causes out-of-bounds issues in these cases. Commit: f60f7bf
• Two instances of pitch-bend effects in some songs, both caused by portamento workarounds... which seem to be no longer needed. Commits: 1042e66, fcc9447
• Use [[fallthrough]] attribute backport. Commit: 6d12e21

Known issues:

• NCSF: Rare clipping in some instruments in some songs. Present from the start, but made worse less obvious (after testing the 2014 plugin) since possibly the 2020 code era. - #1
• Rare subtle popping issues in NCSF. This is actually much rarer than the (now fixed) subtle rare clipping issue. This is also caused by a different bug and not by the clipping fix. #3
• An obscure bug exhibiting slight popping affecting one song, specifically Pokémon Black and White's Title Screen (so far). Has nothing to do with the PLAYER Record oversight, as it predates that bug anyway. #4
• Seeking NCSFs crashes Winamp. #5